The present invention relates generally to a novel device for navigating in narrow, tortuous passageways, such as vascular systems, catheter lumens, and the like, and a method of using the device. More specifically, the invention relates to a novel construction of a medical guidewire and to novel improvements incorporated in a medical guidewire that facilitate the navigability thereof. An improved method of navigability of a guidewire within a lumen is also provided.
Given the increased popularity of non-invasive medical procedures, such as angioplasty and the like, the need for and use of medical guidewires has correspondingly increased. Medical guidewires are used to navigate through narrow, tortuous passageways within a patient in order to reach and to guide appropriate medical instruments, devices, and treatments to a desired treatment site within the patient's body. To do this, the guidewire is inserted into the patient's body through a small access, such as an incision or puncture opening and into the patient's vascular system. The guidewire is progressively fed into the patient's body in an attempt to reach the desired treatment site, while the progression of the wire is monitored by a treating physician, clinician, or other medical professional through appropriate means, such as radiography and the like. In some cases, the medical guidewire may be inserted into and navigated through a catheter lumen, thereby guiding the catheter to an intravascular treatment site.
Because the desired treatment site may be difficult to reach, the guidewire must often be rotated or otherwise steered by the physician as the guidewire is inserted into the patient's body. The physician applies forces to the proximal, out-of-body end of the guidewire hoping that the distal, in-body end of the wire will be influenced to proceed in the desired direction. These proximally applied forces may be rotational forces, axial forces, or forces having other directions to facilitate intravascular navigation of the wire. Specifically, the physician applies forces to the proximal end of the wire which cause the distal end thereof to rotate in a particular direction. In addition, the distal end of the wire may be provided with a coil or tip having a predetermined, preformed curvature which may facilitate steering of the guidewire within the patient's body.
This steering, however, can become quite complex and tedious depending upon location of the treatment site. For instance, if the treatment site is located generally within or proximate to a soft tissue organ, such as the liver, or within the cerebral vasculature, the guidewire may have to be navigated around a number of bends in the patient's vascular system if the treatment site is to be reached. Also, the guidewire may have to be directed into proper branches of the vascular system when the guidewire reaches a juncture of multiple vessels or lumens. By deforming the distal end into a particular configuration, such as a "J"-shape, the treating physician may be able to select an appropriate vascular branch by properly rotating the proximal portion of the guidewire. Rotation of the proximal end induces rotation of the distal end of the guidewire, thereby directing a distal end of the preformed "J" into or towards the proper vascular branch. Once the distal end of the "J" has entered the desired branch, proper application of axial and rotational forces to the proximal end can cause the distal end, and thus, a requisite axial length of the guidewire, to move within the vascular system towards the intended treatment site. But, for this steering method to work, the treating physician must be able to rotate the distal end of the guidewire, and the easier the rotation of the distal end, the easier the procedure progresses.
As the guidewire is navigated around and through an ever increasing number of bends, branches and curves, the contact between the guidewire and an interior surface of the patient's vascular system or an interior surface of a catheter lumen generates friction therebetween, which creates a correspondingly increasing torque or navigation-inhibiting resultant force acting upon the guidewire. Specifically, the contact between the outer surface of the guidewire and a particular lumen interior surface can prevent or resist rotation, often necessary for intravascular navigation, of the guidewire responsive to rotational forces proximally applied by a treating physician. As this resultant force increases, the guidewire becomes progressively more difficult to navigate because of the resistance to steering force transmission along the axial length of the guidewire. Thus, the rotation of the distal end may lag behind corresponding rotation of the proximal end.
Furthermore, if the distal end of the guidewire is curved, or preformed into a "J", the guidewire often must be rotated in order to direct the curved end around a bend or into a desired branch lumen. However, the resultant force on the guidewire, and especially on the distal end, may limit significantly the physician's ability to rotate or maneuver the guidewire, thereby complicating the procedure. Similar steering difficulties can be encountered when the guidewire is located within a catheter lumen within the patient's vascular system. Navigability of the guidewire may also be limited because portions of the distal end of the guidewire have different lubricity, viz. some portions of the guidewire may slide within the vascular or catheter lumen more readily than others.
Many guidewires are provided with flexible coils on the distal ends thereof to improve navigability or pushability of the guidewires in narrow passageways without greatly increasing the stiffness of the wire. But, these coils may kink, thereby inhibiting guidewire navigability. To further improve navigability, some of these coils are coated or overmolded with a lubricous substance. However, coating or overmolding the coils can lock adjacent coils together. Once these coils are interlocked, the range of flexibility thereof, as a whole, may be limited, thereby inhibiting navigability of the guidewires.
These various effects, either alone or in conjunction, can significantly decrease the guidewire's navigability within the vascular or catheter lumen. This decreased navigability of the guidewire may complicate the endovascular procedure being attempted and may limit treatment site accessibility. Accordingly, the present invention provides a novel guidewire structure which solves many, if not all of the above-discussed problems encountered with steering or navigating guidewires within a patient's vascular system or other lumen. The invention also provides a novel sleeve element that can be used to improve the navigability of guidewires, thereby increasing treatment site accessibility. The invention further provides a novel guidewire construction with a distal end having substantially constant lubricity. The invention also provides a lubricous, flexible sheath, separate from a distal end coil, for encompassing the coil, for improving navigability of the guidewire. Furthermore, a novel method of guidewire navigation is also provided.